Make a 2Ys Y-Y plot.
Open PD, and go to plot level: Line tab, set "Symbol/Line interface" as "Gap to Symbol" for both plots.
In PD layer level, Size tab, set Fixed Factor as 0.3 for Layer2, OK.
==>The line gap in legend for C in graph is incorrect.
Click Layer1 than Click Layer2 on Object manager.
==>The line gap of plot legends in Object manager are changed.
Fixed in Origin2024b.